RESUMO
BACKGROUND: Chlorsulfuron resistance and genetic dominance was evaluated in Raphanus raphanistrum genotypes homozygous (122-RR, 376-RR), heterozygous (122-RS, 376-RS) and compound heterozygous (122-R/376-R) for the target-site resistance mutations Ala-122-Tyr and Asp-376-Glu in the AHAS (acetohydroxyacid synthase) gene. RESULTS: At the AHAS level, 122-RR and 122-RS plants exhibited significantly higher I50 values than 376-RR and 376-RS plants, respectively. However, plants of the compound heterozygous genotype (122-R/376-R), showed no difference in AHAS activity compared to the 122-RS genotype but lower activity than the 122-RR genotype, and showed a nearly 400-fold greater I50 value than both genotypes (376-RR and 376-RS) carrying the 376-Glu allele. At the whole-plant level, 100% survival was observed for 122-RR plants at the highest chlorsulfuron dose of 640 g ha-1, yet 376-RR plants showed no survival at 380 g ha-1. Thus, this survival difference resulted in different median lethal dose (LD50) estimates [>640 (122-RR) versus 330 g ha-1(376-RR)]. The effect of chlorsulfuron in reducing aboveground growth of surviving plants also was markedly lower for the homozygous 122-RR (GR50 = 566 g ha-1) than for 376-RR plants (GR50 = 66). Heterozygous plants carrying the 122-Tyr allele (122-RS) exhibited two- and five-fold higher LD50 values than both homozygous and heterozygous plants carrying the 376-Glu allele (376-RR, 376-RS), respectively. Along the difference in plant survival, 122-RS plants also showed four-fold higher GR50 than both 376-RR and 376-RS plants. Survival of plants with the compound heterozygous genotype (122-R/376-R) under increasing chlorsulfuron doses was similar to 122-RR or 122-RS genotypes. However, this compound heterozygous genotype showed two- and six-fold higher LD50 values than 376-RR or 376-RS genotypes, respectively. However, both resistance 122-Tyr and 376-Glu alleles were dominant or nearly dominant over the wild-type susceptible alleles (ALA-122 and ASP-376), and the resistance 122-Tyr allele was dominant over the 376-Glu allele. CONCLUSIONS: These results broaden our understanding of AHAS target-site resistance in R. raphanistrum and strengthens the hypothesis that the AHAS 122-Tyr allele corresponds to a stronger target-site resistance allele than the 376-Glu allele. © 2024 Society of Chemical Industry.
RESUMO
Eragrostis curvula includes biotypes reproducing through obligate and facultative apomixis or, rarely, full sexuality. We previously generated a "tetraploid-dihaploid-tetraploid" series of plants consisting of a tetraploid apomictic plant (T), a sexual dihaploid plant (D) and a tetraploid artificial colchiploid (C). Initially, plant C was nearly 100% sexual. However, its capacity to form non-reduced embryo sacs dramatically increased over a four year period (2003-2007) to reach levels of 85-90%. Here, we confirmed high rates of apomixis in plant C, and used AFLPs and MSAPs to characterize the genetic and epigenetic variation observed in this plant in 2007 as compared to 2003. Of the polymorphic sequences, some had no coding potential whereas others were homologous to retrotransposons and/or protein-coding-like sequences. Our results suggest that in this particular plant system increased apomixis expression is concurrent with genetic and epigenetic modifications, possibly involving transposable elements.
Assuntos
Apomixia/genética , Epigênese Genética , Eragrostis/genética , Variação Genética , Poliploidia , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Elementos de DNA Transponíveis , Regulação da Expressão Gênica de Plantas , Biblioteca Gênica , Genótipo , Polimorfismo GenéticoRESUMO
In many species polyploidization involves rearrangements of the progenitor genomes, at both genetic and epigenetic levels. We analyzed the cytosine methylation status in a 'tetraploid-diploid-tetraploid' series of Eragrostis curvula with a common genetic background by using the MSAP (Methylation-sensitive Amplified Polymorphism) technique. Considerable levels of polymorphisms were detected during ploidy conversions. The total level of methylation observed was lower in the diploid genotype compared to the tetraploid ones. A significant proportion of the epigenetic modifications occurring during the tetraploid-diploid conversion reverted during the diploid-tetraploid one. Genetic and expression data from previous work were used to analyze correlation with methylation variation. All genetic, epigenetic and gene expression variation data correlated significantly when compared by pairs in simple Mantel tests. Dendrograms reflecting genetic, epigenetic and expression distances as well as principal coordinate analysis suggested that plants of identical ploidy levels present similar sets of data. Twelve (12) different genomic fragments displaying different methylation behavior during the ploidy conversions were isolated, sequenced and characterized.